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<?xml-stylesheet type="text/xsl" href="https://community.arm.com/utility/feedstylesheets/rss.xsl" media="screen"?><rss version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:slash="http://purl.org/rss/1.0/modules/slash/" xmlns:wfw="http://wellformedweb.org/CommentAPI/"><channel><title>Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/developer/tools-software/tools/f/keil-forum/26595/conecting-hm55b-compass-sensor-to-mcb2379</link><description> 
Hello. I&amp;#39;m trying to connect the module HM55B (electronic compass)
with MCB 2378. The module operates at 5 volts and I want to connect
FAST GPIO pins that go to 3.3 volts. How I can do? Thank you very
much 
 </description><dc:language>en-US</dc:language><generator>Telligent Community 10</generator><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/126238?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 10:43:03 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:a6909795-2091-4452-93bf-98d94494b096</guid><dc:creator>edPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
The series resistor is when sending data to the processor, not the
other direction. Many processors have body diodes that shorts
overvoltages to VCC. The LPC23xx chips are no exception when
configured as inputs with pull-up or pull-down. The clamp voltage is
a bit above 3.3V so the series resistor will limit the current. If
you have a 10k resitor and we assume that the clamp voltage is 3.5V,
then you have 1.5V and 10k, giving 150uA current.&lt;/p&gt;

&lt;p&gt;
When the LPC23xx GPIO pin is set as output, it will swing between
0V and 3.3V. It is driven strongly, and you can&amp;#39;t just add a pull-up
to draw it from 3.3V to 5V.&lt;/p&gt;

&lt;p&gt;
The pull-up most definitely must be externally - the internal
pull-up will only pull towards VCC, which is 3.3V. When the GPIO pin
is set as tri-state input, it is possible to use an external pull-up
to float the pin all the way to 5V. Since almost all pins on the
LPC23xx are 5V-tolerant, this is safe. But you better check the
datasheet so you really are using one of the signals that are
5V-tolerant. A few pins have special functions that makes their
implementation differ a bit (such as AD inputs, I2C and USB data
signals, ...)&lt;/p&gt;

&lt;p&gt;
So you configure the pin as input with tristate (no pull-up and no
pull-down - the 10 combination from your list). And you set the
output state to low. Then you can switch between pull-up to 5V or
hard drive to 0V by just toggling the output-direction bit. There is
no need to perform any reconfiguration to toggle the pin.&lt;/p&gt;

&lt;p&gt;
The size of the pull-up needs to be adjusted based on the signal
speed and signal trace capacitance to make sure that you get an
acceptable rise time. A pull-up will not give as fast flanks as you
get when actively driving the output pin.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/115844?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 09:02:56 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:a7cac584-6f2e-40bf-aeb8-d9a1bc88c183</guid><dc:creator>pepe perez</dc:creator><description>&lt;p&gt;&lt;p&gt;
Two things.&lt;br /&gt;
1 What is the value of the resistor I put in series when I receive
data from the processor?&lt;br /&gt;
2 You tell me to send data to the compass sensor I have put a pull up
resistor to 5v. I guess it&amp;#39;s outside the processor. But to set the
pin with the PINMODE register, do I have to program it as &amp;quot;10&amp;quot;?:&lt;br /&gt;
00 Pin has an on-chip pull-up resistor enabled&lt;br /&gt;
01 Reserved. This value should not be used.&lt;br /&gt;
10 Pin has neither pull-up nor pull-down resistor enabled.&lt;br /&gt;
11 Pin has an on-chip pull-down resistor enabled.&lt;br /&gt;
Than you for your patience.&lt;br /&gt;
Antonio Moyano&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/115835?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 08:45:36 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:36f04cad-51fc-4815-9fe2-ee1fcdf0c3ef</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;&amp;quot;says the same (5 v).&amp;quot;&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
The ones I found clearly said that the &lt;b&gt;chip&lt;/b&gt; itself was 3V3
- the &lt;i&gt;&lt;b&gt;module&lt;/b&gt;&lt;/i&gt; is supplied with 5V, but has an onboard
regulator that drops this to 3V3.&lt;/p&gt;

&lt;p&gt;
Maybe you have a slightly different variant of &amp;quot;HM55B (compass
sensor)&amp;quot; - so you need to provide links to the actual documents that
apply to the actual version of the actual part that you&amp;#39;re actually
using.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/104060?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 08:41:37 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:d42f5b7b-995c-455a-a81f-92966f0aa185</guid><dc:creator>edPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
A voltage divider is not a good choice when feeding 5V data to a
3V3 device. And it isn&amp;#39;t needed since I have already told you that
the LPC23xx is 5V-tolerant. All you should do is add a series
resistor as current limiter.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/115846?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 08:40:41 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:668e5c5e-1f31-49fc-9768-e3b387561a94</guid><dc:creator>pepe perez</dc:creator><description>&lt;p&gt;&lt;p&gt;
In the data sheet at the beginning says &amp;quot;The sensing device on the
Compass Module is a Hitachi HM55B chip. An onboard regulator and
resistor protection make the 3 volt HM55B chip compatible with 5 volt
supply BASIC Stamp &amp;reg; microcontroller and signal levels&amp;quot;.&lt;br /&gt;
I do not know if it will work when connected to 3.3 volt Vcc, since
then he says that the Vcc is 5 v. It has a voltage regulator.&lt;br /&gt;
If I want to receive data from the sensor, which is the amount of
resistance I have to put in series. Please, Do not get angry with
me.&lt;br /&gt;
Antio Moyano&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/102211?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 08:15:46 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:1bcabe59-9471-4411-8c29-58f0e692f50d</guid><dc:creator>pepe perez</dc:creator><description>&lt;p&gt;&lt;p&gt;
Yes. I have the chip in my hands and I&amp;#39;ve used it with arduino. I
have read the three sheets that I found on the internet and says the
same (5 v). I had thought of two ideas.&lt;br /&gt;
1st to send the data to the sensor using a transistor working in
court and saturation (BC 547).&lt;br /&gt;
2 &amp;ordm; To receive data from the sensor to LPC2378 using a voltage
divider.&lt;br /&gt;
Thank you for your help&lt;br /&gt;
Antonio Moyano&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/78436?ContentTypeID=1</link><pubDate>Tue, 22 Jun 2010 08:08:54 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:51f920ec-7838-48fd-8c27-65bf12944a85</guid><dc:creator>pepe perez</dc:creator><description>&lt;p&gt;&lt;p&gt;
In the datasheet i have read&lt;br /&gt;
this&lt;br /&gt;
Pin Definitions and Ratings&lt;br /&gt;
Symbol Quantity Minimum Typical Maximum Units&lt;br /&gt;
Vcc Supply Voltage 4.8 5.0 5.2 V&lt;br /&gt;
Icc(Ave) Average active supply current* 5 7 mA&lt;br /&gt;
Icc(Pk) Peak instantaneous current** 30 45 mA&lt;br /&gt;
Icc(Sb) Standby supply current 2 3 mA&lt;br /&gt;
GND Ground reference connection 0 V&lt;br /&gt;
VOH Signal high transmit (Dout) Vcc &amp;times; 0.9 Vcc Vcc + 0.5 V&lt;br /&gt;
VOL Signal low transmit (Dout) GND - 0.3 GND Vcc &amp;times; 0.15 V&lt;br /&gt;
VIH Signal high receive (/En, CLK, Din) Vcc &amp;times; 0.8 Vcc Vcc + 0.3
V&lt;br /&gt;
VIL Signal low receive (/En, CLK, Din) - 0.3 GND Vcc &amp;times; 0.12
V&lt;br /&gt;
* Measurement cycle = 80 ms&lt;br /&gt;
** Typical duration is 5 &amp;micro;s&lt;br /&gt;
(1) Din - Serial data input&lt;br /&gt;
(2) Dout - Serial data output&lt;br /&gt;
(3) GND - Ground -&amp;gt; 0 V&lt;br /&gt;
(4) CLK - Synchronous clock input&lt;br /&gt;
(5) /EN - Active-low device enable&lt;br /&gt;
(6) Vcc - +5 V power input&lt;br /&gt;
29123&lt;br /&gt;
I guess you can not use other voltage.&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/65692?ContentTypeID=1</link><pubDate>Mon, 21 Jun 2010 15:00:13 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:482c04d6-d132-4e72-94e5-d2507f255d4a</guid><dc:creator>Andy Neil</dc:creator><description>&lt;p&gt;&lt;p&gt;
&lt;i&gt;&amp;quot;The module [HM55B] operates at 5 volts&amp;quot;&lt;/i&gt;&lt;/p&gt;

&lt;p&gt;
Are you sure?&lt;/p&gt;

&lt;p&gt;
I Googled &amp;quot;HM55B&amp;quot; and found several 3rd-party datasheets using
this chip - and it seems that it&amp;#39;s actually a 3V3 chip.&lt;/p&gt;

&lt;p&gt;
Example:&lt;br /&gt;

&lt;a href="http://www.totalrobots.com/media/parallax/sensors/gps-compass/HM55BModDocs.pdf"&gt;www.totalrobots.com/.../HM55BModDocs.pdf&lt;/a&gt;&lt;/p&gt;

&lt;p&gt;
It is left as an exercise for the student to find the original
chip manufacturer&amp;#39;s datasheet...&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/90476?ContentTypeID=1</link><pubDate>Mon, 21 Jun 2010 14:21:53 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:10f8e36f-83cc-4872-97e9-56a00201a81a</guid><dc:creator>edPer Westermark</dc:creator><description>&lt;p&gt;&lt;p&gt;
LPC2378 have 5V-tolerant pins, so if signals are only sent to the
processor, then it&amp;#39;s enough if you add a series resistor for each
signal.&lt;/p&gt;

&lt;p&gt;
If signals goes from processor to sensor then you need to check if
the sensor can accept +3.3V as logic high with enough safety margin.
If not, then you may have to use a pull-up to 5V and send data by
changing the I/O pin between input (pulled to 5V) and output driven
low. Or buy a level-changer chip and place between. Or put a
transistor between.&lt;/p&gt;

&lt;p&gt;
Standard electronics stuff. You have spent time reading the
datasheet/user manual? And you have read up a bit about mixed-voltage
interfacing?&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item><item><title>RE: Conecting HM55B (compass sensor) to MCB2379</title><link>https://community.arm.com/thread/58349?ContentTypeID=1</link><pubDate>Mon, 21 Jun 2010 11:39:05 GMT</pubDate><guid isPermaLink="false">dd9e70c8-6d3c-4c71-b136-2456382a7b5c:abb94b0d-ab5c-47d9-9975-b7033de5dbdd</guid><dc:creator>pepe perez</dc:creator><description>&lt;p&gt;&lt;p&gt;
Sorry , it&amp;acute;s mcb2378&lt;/p&gt;
&lt;/p&gt;&lt;div style="clear:both;"&gt;&lt;/div&gt;</description></item></channel></rss>